Carolyn J.M. Best

PURPOSE: The development of new cancer drugs is slow and costly. HIV protease inhibitors are Food and Drug Administration approved for HIV patients. Because these drugs cause toxicities that can be associated with inhibition of Akt, an emerging target in cancer, we assessed the potential of HIV protease inhibitors as anticancer agents. EXPERIMENTAL DESIGN: HIV protease inhibitors were screened in vitro using assays that measure cellular proliferation, apoptotic and nonapoptotic cell death, endoplasmic reticulum (ER) stress, autophagy, and activation of Akt. Nelfinavir was tested in non-small cell lung carcinoma (NSCLC) xenografts with biomarker assessment. RESULTS: Three of six HIV protease inhibitors, nelfinavir, ritonavir, and saquinavir, inhibited proliferation of NSCLC cells, as well as every cell line in the NCI60 cell line panel. Nelfinavir was most potent with a mean 50% growth inhibition of 5.2 micromol/L, a concentration achievable in HIV patients. Nelfinavir caused two types of cell death, caspase-dependent apoptosis and caspase-independent death that was characterized by induction of ER stress and autophagy. Autophagy was protective because an inhibitor of autophagy increased nelfinavir-induced death. Akt was variably inhibited by HIV protease inhibitors, but nelfinavir caused the greatest inhibition of endogenous and growth factor-induced Akt activation. Nelfinavir decreased the viability of a panel of drug-resistant breast cancer cell lines and inhibited the growth of NSCLC xenografts that was associated with induction of ER stress, autophagy, and apoptosis. CONCLUSIONS: Nelfinavir is a lead HIV protease inhibitor with pleiotropic effects in cancer cells. Given its wide spectrum of activity, oral availability, and familiarity of administration, nelfinavir is a Food and Drug Administration-approved drug that could be repositioned as a cancer therapeutic.

PURPOSE: After an initial response to androgen ablation, most prostate tumors recur, ultimately progressing to highly aggressive androgen-independent cancer. The molecular mechanisms underlying progression are not well known in part due to the rarity of androgen-independent samples from primary and metastatic sites. EXPERIMENTAL DESIGN: We compared the gene expression profiles of 10 androgen-independent primary prostate tumor biopsies with 10 primary, untreated androgen-dependent tumors. Samples were laser capture microdissected, the RNA was amplified, and gene expression was assessed using Affymetrix Human Genome U133A GeneChip. Differential expression was examined with principal component analysis, hierarchical clustering, and Student's t testing. Analysis of gene ontology was done with Expression Analysis Systematic Explorer and gene expression data were integrated with genomic alterations with Differential Gene Locus Mapping. RESULTS: Unsupervised principal component analysis showed that the androgen-dependent and androgen-independent tumors segregated from one another. After filtering the data, 239 differentially expressed genes were identified. Two main gene ontologies were found discordant between androgen-independent and androgen-dependent tumors: macromolecule biosynthesis was down-regulated and cell adhesion was up-regulated in androgen-independent tumors. Other differentially expressed genes were related to interleukin-6 signaling as well as angiogenesis, cell adhesion, apoptosis, oxidative stress, and hormone response. The Differential Gene Locus Mapping analysis identified nine regions of potential chromosomal deletion in the androgen-independent tumors, including 1p36, 3p21, 6p21, 8p21, 11p15, 11q12, 12q23, 16q12, and 16q21. CONCLUSIONS: Taken together, these data identify several unique characteristics of androgen-independent prostate cancer that may hold potential for the development of targeted therapeutic intervention.

To identify molecular changes that occur during prostate tumor progression, we have characterized a series of prostate cancer cell lines isolated at different stages of tumorigenesis from C3(1)/Tag transgenic mice. Cell lines derived from low- and high-grade prostatic intraepithelial neoplasia, invasive carcinoma, and a lung metastasis exhibited significant differences in cell growth, tumorigenicity, invasiveness, and angiogenesis. cDNA microarray analysis of 8700 features revealed correlations between the tumorigenicity of the C3(1)/Tag-Pr cells and changes in the expression levels of genes regulating cell growth, angiogenesis, and invasion. Many changes observed in transcriptional regulation in this in vitro system are similar to those reported for human prostate cancer, as well as other types of human tumors. This analysis of expression patterns has also identified novel genes that may be involved in mechanisms of prostate oncogenesis or serve as potential biomarkers or therapeutic targets for prostate cancer. Examples include the L1-cell adhesion molecule, metastasis-associated gene (MTA-2), Rab-25, tumor-associated signal transducer-2 (Trop-2), and Selenoprotein-P, a gene that binds selenium and prevents oxidative stress. Many genes identified in the Pr-cell line model have been shown to be altered in human prostate cancer. The comprehensive microarray data provides a rational basis for using this model system for studies where alterations of specific genes or pathways are of particular interest. Quantitative real-time reverse transcription-PCR for Selenoprotein-P demonstrated a similar down-regulation of the transcript of this gene in a subset of human prostate tumors, mouse tumors, and prostate carcinoma cell lines. This work demonstrates that expression profiling in animal models may lead to the identification of novel genes involved in human prostate cancer biology.